1. Field of the Invention
The invention relates generally to electrical connectors and, more particularly, to electrical connectors which are not discretely self-keying.
2. Description of the Prior Art
Whenever two or more plug and socket pairs, each comprising the subassemblies of a connector arrangement, are located adjacent to each other, there is always the possibility that the various connector plugs may not be mated to the sockets for which they were intended, through human error. This is particularly true where these connections are located in difficult access positions, which is often the case in aircraft applications, or the like. If the connectors are of the single cable coaxial type, for example, there is nothing about the connector subassemblies (plug and socket halves) themselves which would prevent mismating, since the corresponding subassemblies are frequently identical parts.
Although there are such things as "polarized" coaxial connectors, these are limited to situations where there are just two coaxial connections to be considered at any one location.
Even in multi-pin connectors, any "keying" provided is usually for rational alignment purposes and cannot prevent the inadvertent mismating of identical plug and socket connector subassemblies.
A particular prior art approach to providing discrete mating, where there is a plurality of coaxial connections to be made in a given location, is described in U.S. Pat. No. 3,194,588, entitled "Key Connector for Plugs and Sockets Having Noninterchangeable Coupling Means." In that device, a "cage-like" device, having internal axially extending ribs, is employed. These ribs are affixed to or are integral with a backing plate and an outer ring. The said backing plate contains a central hole, preferably threaded, to engage the body threads of one subassembly of a connector arrangement (for example, the socket member of a mating coaxial connector pair). An annular groove in those threads may be provided so that the "cage" may be advanced to the point where the threaded hole in the backing plate fits loosely on one part of one connector subassembly. The internal threaded connector body member which would normally engage the threads of the socket member to mate the two subassemblies contains axial grooves in the same number as the aforementioned internal ribs of the "cage" and having the same circumferential spacing. In order to mate the two parts of the connector arrangement, these grooves must engage the cage ribs to permit the required axial closure movement necessary to effect connector mating. Adjacent connectors of the same type may have the keying (coding) provided by the discrete circumferential groove and rib spacings varied to that only like keyed arrangements can be made.
It will be apparent to those skilled in the manufacturing arts that the aforementioned prior art device is expensive to manufacture. Copper-based alloys are normally employed for connector part of the type employed in the connectors with which the invention is concerned, molded plastic or other substitute materials being usually regarded as unsuitable for the application due to the strength and durability considerations.
The manner in which the present invention addresses the general problem of high manufacturing costs to provide a novel improvement in devices of the character described will be evident as this description proceeds.